Hi Allan,
Originally Posted by Allan G
1971 A65 which should use the NPSF thread.

the F stands for fuel(s) and the thread seals completely when tightened. Zccordi g to the service sheets the NPS type threads at least should be of the fuels type (aka dry seal) link showing comparison
Hmmm ... I would've said Triumph and BSA used just NPS thread? I understand the mechanics of "Dryseal" but, steel switch screwing into ally, "Dryseal" theory was never going to work in practice for any length of time.

Originally Posted by Allan G
noticed FEKED list the same switch against both Smith's part numbers for the NPSF and the NPTF
Ye-ea-ah ... Feked is scary-bad:-

. '74-on 60-3719 - Veglia? They were made by Smiths before '79, Veglia only made 'em after Smiths stopped. 24 tpi or 26 tpi? Originals were 27 tpi NPS ... shocked

. Apart from that, the Triumph 60-2133 number is just the standard trade confusion. The original Triumph equivalent of BSA 19-6504 was D1943 (60-1943). Used first on the triple engines, first built in June 1968. That is a taper-thread switch.

. Meriden then caused the monumental part numbers confusion by printing D2133 in the '69 twins' parts books but fitting some of their early '69 ones with taper-thread switches. When the Triumph triples changed to straight-thread switches is recorded as January 1969; Meriden issued a new parts book around the same time, with D2133 for the switch ... Meriden failed to record when they changed the twins from taper- to straight-thread but afaict before they started using the date-code-5-figure-number VIN format in October 1968.

. Educated guess says Rocket 3's changed from taper- to straight-thread switch (19-6504 to 19-6508) around the same time as the Tridents; however, is there any record of when the '69 BSA twins did?

Originally Posted by Allan G
Draganfly (where I got mine from) don't distinguish either way.
Draganfly is just confused (reflecting they're fairly recent Triumph and BSA dealers) - if you look at their entry for Triumph 60-2133, it's the same switch as BSA 19-6508 but the 60-2133 entry says it's taper-thread, that - as I say - is just the general trade confusion over the part numbers. facepalm If you want an NPS switch for your '71 A65, order 60-3719 from the confused trade ...

Originally Posted by Allan G
would imagine there is just as much meat on an A65 as there is surrounding the threads on a triumph casing.
Mmmm ... I'm only familiar with the switch position on a '70-on single; if the A65's similar, much more "meat" than a Triumph timing cover.

[Linked Image from cdn.shopify.com]

... gives an idea of how little "meat" there is around a Triumph twin's OP switch hole ...

Hth.

Regards,